Albian – Cenomanian Palynofacies and Palynostratigraphy of Ctp-1 Well, Offshore Tano Basin

Abstract

This study describes and identifies palynomorphs (spore/pollen and dinoflagellates) from different levels of the CTP-1 well succession in the offshore Tano Basin in order to establish palynostratigraphy of the studied sediments. The palynomorphs are used as an age tool for the sediments after comparison with other species or sediments reported from other parts of the world, especially the North Gondwana Province (ASA) region. Sedimentary Organic Matter is used to establish palynofacies assemblages to interpret paleoenvironmental and paleoclimatic conditions at the time of deposition, infer kerogen type and establish thermal maturity of the sediments of the succession to infer the hydrocarbon potential. Based on the first appearance datum (FAD) and the last appearance datum (LAD) of stratigraphically important species, two miospore assemblage zones have been suggested for the sediments. The zones are (I) The Elateropollenites jardinei- Ephedripites irregularis-Reyrea polymorphus zone and (II) The Elaterosporites protensus-Sofrepites legouxiae-Afropollis jardinei zone. After comparison with similar assemblages from other parts of the world, the Albian-Cenomanian age has been suggested for the sediments. Based on the similar microfloral assemblage observed from the Ghanaian assemblage to those of the Africa-South America (ASA) province, the paleofloral province suggested for the miospores of this study is the Albian-Cenomanian Elaterate Province. Miospore assemblages indicate that deposition of the sediments took place in a semi- arid to arid climatic conditions in a coastal or nearshore environment. The dinoflagellate assemblage corroborates the environment of deposition as marginal marine/nearshore environment. Four palynofacies associations (P-1, P-2, P-3, and P-4) have been identified under the following contortion. P-1 and P-2 are characterized by marginal dysoxic-anoxic basin and shelf to basin transition, P-3 is characterized by a distal suboxic- anoxic basin environment and P-4 is characterized by distal dysoxic-anoxic shelf and distal dysoxic-oxic shelf. Thermal maturity based on exine colours of psilate spores (Cyathidites) indicates mature and immature organic matter of Kerogen Type II (oil prone) with TAI values of 2+, 3-, 3, 3+ and Type III (gas prone) with TAI values of 1+, 2-, 2 respectively.